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FW: Unified PMD vs. Unified PHY


With "Brainstorming Over" cleared up, I would like to address another
concept in your original note that I think is causing some grief.

In your comment, you identify a time line for information exposure that you,
rightfully, argue is not significantly different for SLP, 64b/66b, and Hari

But, even if the schedules where skewed so that the overlapped, a
significant difference would still remain. Let me explain.

XAUI (Hari) builds on a previous knowledge base of information which is not
detailed in any of the presentations. This detail is found in the Fibre
Channel and the 802.3z standards themselves. When Rich or Howard shows a
high level representation using an "8B/10B" coding layer as a basis, the
committee knows exactly what that means. They know exactly how SERDES will
function; exactly how bit and byte synchronization will be accomplished,
etc. The presentations therefore show only the additional information
required to complete the picture (e.g., how lane to lane synchronization is

The case of 64b/66b follows this to a degree. In this case, a number of us
who have been "around for a while," can take the information provided and
make the jump to the solution. For me, I prefer to see a little bit more
detail, but there is a "degree of comfort" with what has been presented to

In the case of SLP, the gap to be bridged is a bit larger (perhaps a gross
understatement). Per my note last week, I have greatest struggle with the
bridge is to the multilane solution (a problem the 64b/66b doesn't have to
deal with since it assumes the XAUI direct). 

The problem is that for the SLP to be at an equivalent level to the XAUI
presentations, it needs to define those same things that are included in the
XAUI references (explicit or not). Warning: Opinion On. If you will, XAUI is
a bottom up proposal based on FC and 802.3z. SLP is a top down that has not
had the time to fill in the details yet. Opinion off.

Last week, I had a discussion, off line, with Kameran on this topic. I
expect that he is working on these issues and would welcome help building
the complete technical structure for the SLP proposal. In my mind, this
would include the complete information on how serial, parallel, WWDM, and
PAM implementations would be supported. A list of all the assumptions for
each of the PMDs, PMAs, etc. Each PMA, for instance, should show how bit and
byte synchronization should be accomplished and maintained (what is the
hysteresis mechanism?). The PCS should show how lane synchronization is


> -----Original Message-----
> From: Truman, Thomas E (Tom) [mailto:truman@xxxxxxxxxx]
> Sent: Wednesday, March 15, 2000 4:04 PM
> To: 'Jonathan Thatcher'
> Subject: RE: Unified PMD vs. Unified PHY
> Thanks for the clarification -- I agree with your statements, then.
> Cheers,
> Tom
> -----Original Message-----
> From: Jonathan Thatcher 
> [mailto:Jonathan.Thatcher@xxxxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, March 15, 2000 4:16 PM
> To: Truman, Thomas E (Tom)
> Subject: RE: Unified PMD vs. Unified PHY
> Tom,
> We must have very different definitions for the word 
> "brainstorming." I was
> taught that brainstorming was, according to Webster, "a group
> problem-solving technique that involves the spontaneous 
> contribution of
> ideas from all members of the group" where (not in Webster) 
> criticism is
> withheld. It is a time to encourage all ideas and allow all 
> members of the
> group to participate without fear of judgment.
> To me, your criticism is proof positive that the "brainstorming 
> phase" is in
> fact over. :-)
> jonathan
> p.s. "Brainstorming being over" does not mean that the group 
> becomes "brain
> dead."
> > -----Original Message-----
> > From: Truman, Thomas E (Tom) [mailto:truman@xxxxxxxxxx]
> > Sent: Wednesday, March 15, 2000 2:11 PM
> > To: 'Jonathan Thatcher'; HSSG
> > Subject: RE: Unified PMD vs. Unified PHY
> > 
> > 
> > Jonathan,
> > 
> > My reading of the timeline presented in the January 2000 intro
> > (
> > ntro_0100.pdf)
> > indicates that July 2000 marks the acceptance of the last new 
> > proposal, and I'm compelled to push back on your statement
> > that brainstorming work is "OVER".
> > 
> > Looking back over the archives, it was at the November meeting
> > that HARI was introduced, and in January 64b/66b was added. Both
> > the UniPHY and SLPs proposal were introduced in March.
> > 
> > Clearly a large set of the 802.3ae members are still brainstorming,
> > and should continue to thrash out the merits of these 
> proposals until
> > the July vote. There is a lot of work to be done in the meantime and
> > we'll need the full 3.5 months.
> > 
> > Regards,
> > Tom Truman
> > 
> > -----Original Message-----
> > From: Jonathan Thatcher 
> > [mailto:Jonathan.Thatcher@xxxxxxxxxxxxxxxxxxxx]
> > Sent: Wednesday, March 15, 2000 12:41 PM
> > To: HSSG
> > Subject: RE: Unified PMD vs. Unified PHY
> > 
> > 
> > (... deleted ...)
> > Now that the brainstorming phase of the work IS OVER, all of us 
> > need to do
> > some soul searching. We have had a year to position our various 
> > proposals
> > 
> > (... deleted ...)
> >  
> >   
> >